1. Field of the Disclosure
The present invention is generally drawn to ceramic particulate material and processes for forming same. In particular, aspects of the present invention are drawn to alumina ceramic particulate material.
2. Description of the Related Art
Alumnus particulate material, including hydrated aluminas, transition-phase aluminas, and the high temperature phase of alumina, alpha-alumina, have been commonly used in various industrial applications, including use as fillers, raw materials for ceramic bodies and abrasives, among many others. Certain industries, including the abrasives industry, can use the particulate material in loose form, deploying the material in a free-abrasive slurry, a coated abrasive, or a bonded abrasive, for example. Within the context of abrasive slurries, a particular species of slurries is utilized for chemical mechanical polishing (CMP), in which the abrasive slurry not only has mechanical properties of abrasion, but also desirable chemical properties assisting in the mechanical removal of material from a work piece.
Other industries take advantage of alumina particulate material as a raw material forming various ceramic bodies. Often times, it is desired that the ceramic bodies are sinterable to a desired density under a confined thermal budget, including limitations on maximum sintering temperature and dwell times. Limitations on the thermal budget may be placed on processing due to temperature limitations on other components in case of a composite, and due to processing costs, for example. However, particular thermal processing parameters are typically balanced against the degree of sintering required by the particular component, and attendant densification.
In light of the forgoing, it is particularly desirable to provide ceramic particulate material, including alumina particles, that has properties which may be advantageous for deployment in various industries including those requiring sintered bodies, abrasives applications, as in the particular case of polishing slurries, and filler applications.
Alumina particulate technologies are mature and the state of the art is well developed. Among the state of the art, particular processing methodologies enable the formation of a wide range of alumina particulate morphologies, which include particular specific surface area (SSA), particle size distribution, primary particle size and secondary particle size characteristics. For example, one process methodology relies upon utilization of a salt raw material for forming the alumina particulate material, such as an aluminum nitrate salt solution. Such solution may be seeded to aid in the transformation of the aluminum salt into the finally desired crystal phase, such as alpha phase alumina. Examples of such approaches are shown in, for example, U.S. Pat. No. 6,841,497 as well as U.S. Pat. No. 7,078,010.
As exemplified by the forgoing patents, nanosized alpha-alumina particulate material may be successfully formed through synthesis based upon utilization of a salt raw material. However, the morphologies and powder characteristics enabled by such approaches are somewhat confined. Other approaches utilized high temperature treatment of an alpha-alumina precursor, such as a hydrated alumina including boehmite, in the presence of seeds, such as alpha-alumina seeds. Such approaches have been successful in the formation of alpha-alumina particulate material for a wide range of applications, but also have limited particle morphologies and characteristics.